Manufacture of heat exchange structures



y 9, 1961 R. w. ABBOTT 2,983,300

MANUFACTURE OF HEAT EXCHANGE STRUCTURES Filed May 25, 1959 4Sheets-Sheet 1 F'IGI INVENTOR ROY W. ABBOTT BY W H l 5 ATTORNEY May 9,1961 R. w. ABBOTT 2,933,300

MANUFACTURE OF HEAT EXCHANGE STRUCTURES Filed May 25, 1959 4Sheets-Sheet 2 F'IG.2

INVENTOR F- 3 R'ov w. ABBOTT H l 5 ATTORNEY May 9, 1961 Filed May 25,1959 FM IO R. W. ABBOTT MANUFACTURE OF HEAT EXCHANGE STRUCTURES 4Sheets-Sheet 3 INVENTOR.

ROY w. ABBOTT ATTORNEY y 1951 R. w. ABBOTT 2,983,300

MANUFACTURE OF HEAT EXCHANGE STRUCTURES Filed May 25, 1959 4Sheets-Sheet 4 FIG. 6

FIG. )2

INVENTOR.

ROY w. ABBOTT HIS ATTORNEY United States Patent MANUFACTURE OF HEATEXCHANGE STRUCTURES Roy W. Abbott, Jetfersontown, Ky., assign'or toGeneral Electric Company, a corporation of New York Filed May as, 1959,Ser. No. 815,598

12 Claims. c1. 153-2 The present invention relates to the manufacture ofheat exchange structures and more particularly to the manufacture ofsuch structures from heat exchange tubing of the type including acentral tube surrounded by a multiplicity of narrow individual finsections, or

. spine sections, extending from the surface thereof.

One form of heat exchange tubing with which the present invention isparticularly concerned is manufactured by helically wrapping onto atubing an 'L-shaped strip of fin stock with one leg of the L-shaped finbeing in flatwise engagement upon the tubing and with the other leg ofthe L-shaped fin being serrated into a plurality of individual orspine-like fin sections. The spinelike fin sections spread duringwrapping so that each section extends radially outward from the tubing.For ease of description, the above-described type of heat exchangetubing will hereinafter be referred to in the specification and claimsas spine fin tubing. Because of the manner of forming the spine sectionsof spine fin tubing, they are easily bent or collapsed whenever force isapplied upon the individual spine sections in the direction normal tothe bend in the L-shaped fin structure. More specifically, these spinesections are easily bent or collapsed Whenever they encounter a forceapplied in a direction along the axis of the tubing. For this reason,much difiiculty is encountered in fabricating spine fin tubing into heatexchange structures having a plurality of passes of tubing. That is, itis difficult to wind or form overlapping coils of this type of heatexchange tubing one upon the other because the outwardly extending spinesections of the adjacent passes of tubing interlock during the windingof the coils and the winding or coiling force along the axis of thetubing causes these interlocking spine sections to collapse or bend overagainst the tube surface. Because a component of force along the axis ofthe tubing is always present during a winding or coiling operation, onecoil of tubing cannot be formed directly over a previous coil. 7

It is an object of the present invention to provide an improved methodfor fabricating coiled heat exchange structures from spine fin tubing,

It is another object of the present invention to provide a method ofmanufacturing a heat exchange structure from spine fin tubing in whichthe structure comprises at least one row of overlapping coils graduallyincreasing in circumference with the individual fin sections of theadjacent coils interlocking to maintain the structure in substantiallyflat shape.

It is a further object of the present invention to provide a machine formanufacturing a heat exchange 2,983,300 Patented May 9, 196 1 structurehaving a plurality of overlapping coils of spine fin tubing.

Further objects and advantages of the invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize the 'invention will be pointed out with particularity inthe claims annexed to and forming a part of this specification.

In carrying out the objects of the present invention there is provided amethod of manufacturing a heat exchange structure comprising the stepsof providing a length of spine fin tubing, forming this length of spinefin tubing into a plurality of helical coils with the first coil ofrelatively small circumference and With each succeeding coil increasingin outer circumference over that of the preceding coil but having aninner circumference slightly less than the outer circumference of thepreceding coil, and compressing the coils axially relative to each otherto telescope the inner coils into the outer coils with the spinesections of the adjacent coils sliding between each other andinterlocking to hold the coils overlapped in a single row andsubstantially fiat in shape.

As a further aspect of the present invention there is provided a machinefor manufacturing a heat exchange structure from a length of spine fintubing according to the above-described method. The machine comprises apyramid-shaped coil forming fixture having a collapsible coil formingmember. The coil forming member comprises a length of spring-likematerial helically wound into a plurality of coils each increasing incircumference over the previous coil and overlapping the previous coil.The coil forming member presents a continuous peripheral windingsurface, with the surface of each successive coil being radiallydisplaced from the surface of the preceding coil by an amount slightlyless than the diameter of the spine fin tubing to beformed. On the smallcircumference end of the coil forming member, means are provided forattaching the end of a length of spine fin tubing. The fixture ismounted for rotation by a suitable source of power in order to 'wind thelength of spine fin tubing thereon into a plurality of helical coilsgradually increasing in circumference. Means are provided for collapsingthe coil forming member so that the transverse edges of the respectivecoils cooperate to provide a fiat pressing surface normal to the axis ofthe coiled heat exchange tubing. Adjacent the small end of the coilforming member is a compression means or compression surface normal tothe axis of the coil forming member which cooperates with the collapsedcoil forming member to compress the coiled tubing so that the innercoils of tubing are telescoped into the outer coils of tubing to form aheat exchange structure having a substantially fiat shape with the spinesections thereof interlocking.

For a better understanding of the invention, reference may be had to theaccompanying drawings in which:

Fig. l is a plan view of a machine for manufacturing a heat exchangeraccording to the method of the present invention;

Fig. 2 is a partial view of the machine of Fig. 1 showing the formingfixture in the collapsed state and pressing the tubing into a single rowof coils;

Fig. 3 is a partial cross-sectional view of the machine '5 of the member6 by rotating the wrapping fixture.

of Fig. 1 showing in detail the mechanism for collapsing the coilforming member;

Fig. 4 is an elevation view of a machine having two coil forming membersarranged to form a heat exchange structure having two rows of coils;

Fig. 5 is an elevation view of the machine of Fig. 4 showing spine fintubing helically wrapped onto the coiling members of the machine;

Fig. 6 illustrates the machine of Fig. 4 with the coiling memberscollapsed and compressing the spine fin tubing intotworowsofcoils; 4 r

Fig. 7 is an elevation view taken along line of Fig. 6, showing the flatcoil structure formed by the machine of the present invention; Y

a Fig. 8 is a side elevation view showing a core of spine fin tubingadapted for use in the machine of'Fig. 4 for manufacturing a heatexchange structure having two rows of coiled spine fin tubing;

--Fig. 9 is a cross-sectional view of the core taken along line 99ofFig. 8; e

Fig. 10 is a partial cross-sectional" view of the-core showing one sideof the core wrapped transversely to the reverse bend in the core;

Fig. 11 illustrates two adjacent heat exchange tubes with the spinesections thereof extending radially outward therefrom and illustratingthe manner in which the fin sections interlock; and

Fig. 12 is a top view of portions of the heat exchange tubes of Fig. 11further illustrating the manner in which the spine sections interlockduring compression of the coils of tubing.

Referring now to Fig. 1 there is shown a machine for winding heatexchange tubing of the spine fin type into a plurality of helical coilsand for pressing these coils into a single row or pass of coiled tubing.The illustrated machine comprises a support or base structure 2 whichsupports the machine for rotation about an axis normal to the support.The main portion of the machine includes a winding or coiling fixture 3including a "backing plate 4 which supports a pyramid-shaped coilformingmember 6. The coil-forming member 6 comprises a length of spring-likematerial of rectangular cross-section which is coiled into a pluralityof helical coils gradually increasing in circumference from one end tothe other with the largest coil of the member being connected to thebacking plate 4. The outer surface or peripheral surface of coil formingmember 6, generally designated 5 in the drawings, forms a smooth coilwinding surface for winding a length of spine fin tubing 7 onto the coilforming member to form a plurality of helical coils of tubing graduallyincreasing in circumference from one end to the other.

As may be seen in Fig. 1, the coil forming fixture 3 is supported forrotation by the base 2 which supports a spindle. 12 in cantileverfashion for rotation about a horizontal axis. A length 7 of heatexchange tubing is first attached to the inner or smallest coil(obscured in Fig. l by the tubing 7) of the coil forming member 6 and iscontinuously wrapped onto the peripheral surface In the illustratedembodiment of the invention, power is supplied by a motor 14 forrotating the wrapping fixture 3. More specifically, the motor 14supplies power through a gear 15 to the drive sprocket 16 which isconnected by means of a chain 17 to the drive sprocket 18 positionedaround the spindle 12 of the wrapping fixture.

1y, there is provided a feeding head 21 supported by a shaft 22 and aworm shaft 23. Rotation of the worm shaft 23 causes the feeding head 21to move to the left or tothe right according to the direction ofrotationof 4 the worm. Rotation of the worm shaft 23 is provided through wormsprocket 25 and a chain 24 which extends around the motor drive sprocket16. In the illustrated embodiment of the invention, the length 7 ofspine fin material is attached to the smallest coil of the coilingfixture 3 and the coil is rotated so that the upper portion of thefixture is rotated toward the viewer. The heat exchange tubing 7 is thenwrapped around the surface of the coiling member and continuously movedto the right by the feeding head '21. [This movement of the feeding head21 to the right causes the tubing to wind around the helical outersurface 5 of the coiling member 6 as the coiling surfaces are presentedto the tubing.

As may best be seen in Fig. 3, the machine is provided with means forcollapsing the coiling member 6 so that the transverse edges 8 of theforming coils present a pressing surface in a plane normal to the'axisof the membeL-"More specifically, therev are provided a plurality ofstop members 30, 31, 32, 33, 34 and 35, which are attached to theindividual-forming coils of the springlike member 6 and cause theinnermost forming coils of the member to telescope into the outermostforming coils as the backing plate 4 is moved toward the narrow or lefthand portion of the fixture, as seen in' Fig. 3. A

pair of hydraulically operated pistons 37 (not shown in Fig. 3) forcethe backing plate 4 to the left so that the forming coils of thepyramid-shaped member 6 are telescoped into each other and arranged in aplane normal to the axis of the member.

Still referring to Fig. 3, the stop 351s connected to the smallestforming coil 38 of the spring-like member 6 and prevents movement ofthis forming coil 38 when the backing plate is moved to the left. Theremaining stops 30, 31, 32, 33 and 34 each include a mos/able rod 28which is connected at one end to a coil of the coiling next. to smallestcoil 39 of the coil forming member 6,

permits movement of this forming coil 39 to the left only far enoughtocause it to completely overlap the smallest forming coil 38 so that thetransverse edges 8 of both coils are in alignment. The rods 28'arc eachstopped in succession by engagement of the respective adjusting nuts 29with ends 36a of the stop brackets. When the adjusting nut 29 of eachstop member engages the end 36a of the stop bracket the coil attached tothe end of the rod 28 has moved to the left sufficiently to align itstransverse edge 8 with the edges of the previously stopped coil. In thismanner the stop members cause the larger forming coils to move intooverlapping relationship with respect to the inner or smaller formingcoils as thebacking plate 4 is moved toward the left. After all of thecoils have been stopped in their movement to the left, the backing plate4 moves over the-spring-like coiling member with the coiling membercompletely collapsing into the cavity 46 of the backing plate.

Referring now to Figs. .1 and 2, in order to compress i the helical coilof spine fin tubing, on the winding fixture during movement of thebacking plate 4 to the left, there is provided a compressing means inthe form of a plate 41 which is disposed normal to the axis of thecoiling member 6 adjacent the smallest coil 38 of the member 6. Theplate 41 remains stationary with respect to the coiling fixture 3 and,as-the successive forming coils of the spring-like member 6 arecollapsed, the transverse edges 8 of each of the forming coils push theformed tubing off of the surface 5 of the preceding forming coiltherebyforcing the tubing against the plate 41. When the backing plate 4is moved to its furthermost position to the left and the spring-likemember 6 is completely collapsed, the coils of spine fin tubing arepressed into a single pass or row of spiral coils 26. The coilingfixture 3 completely collapses into the cavity 40 so that the dis tancebetween the compression plate 41 and the backing plate 3 is equal to thediameter of the heat exchange tubing 7. After the coiled tubing iscompressed, the compressing plate 41 is pivoted away from the fixture 3on a hinge (not shown) and the single row of tubing is easily removedfrom the fixture. The collapsed coiling member 6 is then expanded topermit forming of another length of tubing thereon.

Referring now to Figs. 11 and 12, there are shown two adjacent sections7a and 7b of spine fin tubing which are arranged in the position theyoccupy after the tubing has been compressed into a single row structurebetween the backing plate 4 and the compressing plate 41, as illustratedin Fig. 2. The spine fin tubing includes a central tube 9 having aplurality of radially extending fin sections 10 connected by a baseflange 11 wrapped thereon. As will be noted in Figs. 11 and 12, the twosections are positioned closely enough together that the spine sections10 overlap by an amount indicated by the letter x. As has beenpreviously pointed out, these fin sections resist bending in a directionparallel to the fold 15 formed between the base flange 11 and the finsection 10 but are easily bent by any force directed against the finsections 10 normal to the fold 15 or in a direction parallel to the axisof the tubing 9. If this spine fin tubing is wound With each successivecoiloverlapping the previous coil, the spine sections interlock duringwinding and the winding force, which is along the axis of the tubing,causes the spine sections to collapse or bend about the told 15, so thatthey lay substantially flat against the tubing.

By first forming the coils of tubing into a helical structure and thencompressing the coils in the manner of the present invention, a fiatcoiled heat exchanger is fabricated without causing the individual spinesections to bend over against the tubing. This is because the coils oftubing, as represented by sections 7a and 7b, are moved with respect toeach other in the direction indicated by the vertical arrows in Fig. 10so that the spine sections 8 resist bending and merely slide into thespace between the successive wraps of fins. Some of the "spine fins oneach of the sections 7a and 7b collide during the compression operationand these are forced to give slightly one way or the other to permit thesections to move into alignment. However, the fin sections 10 only giveslightly and are not caused to bend over against the tubing. As isevident from Fig. 12, the overlapping spine fins do not align exactlyand become interlocked during the compression operation. Thisinterlocking action prevents the sections from moving apart after thecompressive force is removed.

In order to cause overlapping of the individual spine sections it isnecessary to wind the successively larger coils of spine fin tubing sothat the inner circumference of each successive coil is slightly less orsmaller than the outer circumference of the preceding coil; This isaccomplished by making the radial distance between the coiling surfaces,such as surfaces a and 5b of Fig. 1, slightly less than the overalldiameter of the spine fin tubing to be formed. However, the amount ofoverlap between adjacent passes or sections of tubing, as shown by theoverlap designated x in Fig. 11 cannot be greater than the length of anindividual spine section 10. Thus, in this specification and in theclaims annexed hereto, the terms slightly smaller or small amount mean adistance no greater than the length of an individual fin section whenthese terms are applied to the radial displacement between the outer andinner circumferences respectively of successively wound coils or whenapplied to the radial displacement between the outer surfaces ofsuccessively larger forming coils of the coiling member 6, such assurfaces 5a and 5b, in Fig. 1. Thus, by the statement that each coilinner surface is radially displaced from the outer surface of thepreceding coil by a small amoun less than the diameter of the spine fintubing, it is meant that the radial displacement is less than theoverall diameter of the spine fin tubing by an amount no greater thanthe length of a fin section.

Referring now to Figs. 4, 5 and 6 there is shown a second machine,incorporating the fabricating concepts of the present invention, inwhich the coiling fixture comprises two oppositely arranged coiling orspring-like members 6 disposed to permit simultaneous winding of twolengths of spine fin tubing onto the fixture as the fixture is rotatedin one direction. One length of tubing is formed exactly as thatpreviously described with respect to the machine of Fig. 1 while theother length of tubing forms an identical coil except that it is pitchedin the opposite direction. The coiled lengths of tubing are helicallywrapped from the center in opposite directions and, in the illustratedembodiment, are connected at their innermost ends to form a continuoustubular member narrow in its center portion and progressively increasingin circumference toward both ends. Each of the oppositely disposedcoiling members 6 are collapsible when the backing plates 4 of thecoiling fixture are moved toward one another. Movement of the plates 4by the hydraulic pistons 37 compresses the coiled tubular member andtelescopes the inner coils within the outer coils to form two rows 26and 27 of spiral coils disposed in substantially fiat shape.

Fig. 6 illustrates the machine with the forming members collapsed andpressing the tubing into two adjacent spiral rows having an overallthickness slightly less than twice the diameter of the spine fin tubing.As pointed out with respect to the machine of Fig. l, the transverseedge of each coil of the coil forming member pushes or forces thepreviously formed coil of spine fin tubing off of the surface of theprevious coil of the forming member so that each successively largercoil of tubing is forced over the outer circumference of the previouslyformed coil of tubing. The spines of the adjacent coils of heat exchangetubing interlock during the pressing operation and force the structureto maintain a substantially flat shape.

In Fig. 4, it will be noted that a preformed core section 43 of spinefin tubing is positioned between the oppositely arranged coiling members6. Because it is desirable to have heat exchange tubing fill most of thespace bounded by the outermost coil of the heat exchanger, the presentinvention contemplates use of a preformed core section 43 to form theinnermost turns of the heat exchanger, The core section 43 isnecessarily formed into a plurality of very tight turns by using aninner mandrel which prevents the tubing from collapsing on itself in thearea of the turns. The manner or methods of forming tight turns in heatexchange tubing by means of inner mandrels are well known in the art andany suitable method may be employed.

The core section 43 which is more clearly illustrated in Figs. 8, 9 and10, comprises a short length of tubing having a reverse bend 44 at itscenter portion and then having a few turns of tubing wrapped upon itselfin a direction transverse to the reverse bend 44. Thus, referring toFigs. 8 and 10, the length of tubing on opposite sides of the reversebend 44 is again provided with bends 46 of relatively short radius whichreverse the tubing so that it passes over the reverse bend 44 in thecenter of the tubing. The tubing is then formed into larger radius bends47 with the open ends 50 of the tubing folded to overlap the innerportions of the core.

In forming the bends 46 and 47, it is convenient to make the bends overa form which makes small openings 48 and 49 on the under side of thebends. These openings 48 and 49 may be used for mounting the core 43onto the coil winding machine. Thus, as may be seen in Fig. 7, whichshows a cross section of the machine and a coil of tubing, the core43-is mounted on pegs or rods 51 and 52 which extend from one of thecoil winding members 6 of the machine. In order to insert the core 43onto the pegs, the opposite sides of the machine are separated. Afterthe core has been inserted the opposite sides of the machine are broughttogther again into their Winding positiorn Lengths 7 ofheat exchangetubing are then brazedor connected in any suitable manner to the openends 50 of the core member 43. These lengths 7 of heat exchange tubingare then fed through a pair of feeding heads (not shown) .which feed thelengths of tubing onto the coiling surfaces of the coiling fixtures 3 asthe coiling fixture is rotated. The coil forming members 6 then form thecoil structure illustrated in Fig. 5, with the core 43 arrangedto fillthe center of the heat exchange structure. Then the opposite coilingfixtures are collapsed and the helically wound outer coils of heatexchange tubing 7 are pressed inwardly toward the center of the fixture.The smallest coils 42 of tubing formed on the coil forming members 6 arepressed over the core 43 which then forms the center of the structure asis illustrated by the spiral coiled structure shown in Fig. 7.

The abovedescribed machines 'each utilize in their method of formingheat exchage structures from lengths of spine fin tubing, the steps offirst helically winding spine fin tubing into a plurality of coils eachincreasing in circumference over the previous coil and then, compressingthe helically formed coils, telescoping the inner coils into the largercoils, forming a row, or rows, of

tubing each of which is held in substantially flat shape by theinterlocking action of the spine fin sections. It is this concept oftelescoping the inner coils into the larger coils in a direction normalto the major axis of the tubing, or along the line parallel to the bendin the L-shaped spine fin sections, that enables the heat exchangestructure to be formed in this manner. Obviously, this method of formingthese structures can be performed on fixtures other than thosedescribed. For instance, the helical coil may first be formed on anoncollapsible coil forming member having a substantially smooth coilingsurface and then removed from this coiling member and placed in a pressadapted to press the opposite ends of the coiled structure together totelescope the smaller coils into the outer coils. It is, however,important that the length of heat exchange material be first coiled intoa plurality of helical coils with subsequent coils gradually increasingin circumference over the previous coils and with each subsequent coilhaving a circumference slightly smaller than the outer circumference .ofthe preceding coil so that, when the coiled structure is compressed, thespine fins of the adjacent coils interlock and hold the structure insubstantially flat shape. i

By the present invention, there has been provided a method forfabricating coiled heat exchangestructures from spine fin material whichmethod completely elimi nates the collapsing or bending of the spinesections of the tubing in the overlapped portions of the structure. -Asa further aspect of this invention, a machine is provided upon which thesteps called for in the above-mentioned method are easily carried outand adapted to mass production manufacturing techniques.

While in accordance with the patent statutes therehas been describedwhat at present is considered to be the preferred embodiment of theinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made therein without departing from theinvention and it is, therefore, the aim of the appended claims to coverall such changes and modifications as fall within the true spirit andscope of the invention.

.What I. claim as new and desire to secure by Letters Patent of theUnited States is: a a

l. The method of manufacturing a heat exchange structure comprisingprovidinga length at heat exchange tubing having a multiplicity of spinesections extending radially outward from the surface thereof, formingsaid length of heat exchange tubing into a plurality of helically woundcoils withsubsequent coils being greater in circumference than eachpreceding coil but each subsequent coil having an inner circumferenceslightly smaller than the outercircumference of the preceding coil, andcompressing said coils axially relative to each other thereby totelescope the outer helical coils onto the inner helical coils'to. forma heat exchange structure having a single row of coils with said spinesections of said adjacent coils interlocking to maintain said structurein substantially flat shape.

2. The method .of manufacturing a heat exchange structure comprising thesteps of providing a length of'heat exchange tubing having amultiplicity of spine sections extending radially outward from thesurface thereof, forming said length of heat exchange tubing into ahelically coiled member including a plurality of helically wound coilswith each subsequent co l having a greater outer circumference than thepreceding coil but with the inner circumference of each subsquent coilbeing radially disposed a small amount less than the outer circumferenceof the preceding coil and compressing one end of said coiled memberrelative to the other end thereby to telescope the outer helical coilsonto the inner helical coils to form a heat exchange structure having asinglerow of coils with said spine sections of said heat exchange tubinginterlocking to maintain said coils in said single row. i

3. The method of manufacturing a heat exchange structuref comprising thesteps of providing two lengths of heat exchange tubing having amultiplicity of spine sections extending radially outwardfrom thesurfaces thereof, forming each of said lengths of heat exchange tubinginto a plurality of helical coils with each subsequent coil having agreater outer circumference than the outer circumference of thepreceding coil but with each subsequent 'coil having an innercircumference less .than the outer circumference of the preceding coil,connecting the innermost ends of said lengths of tubing to form acontinuous tubular member narrow in its center portion and progressivelyincreasing in circumference toward both ends, and compressing the endsof said tubular member relative to each other thereby to telescope theouter helical coils onto the inner helical coils to form a heat exchangestructure having two rows of coils connected at their inner ends andwith said spine sections of said heat exchange tubing interlocking tohold said coils in alignment and to maintain said structure in asubstantially fiat shape. 1

'4. .The method of manufacturing a heat exchange structure comprisingthe steps of providing a lengthof heat exchange tubing having amultiplicity of spine sections extending radially outward from thesurface thereof, reverse bending said length of heat exchange tubingforming equal portions of said tubing on opposite sides of the bend,forming said equal portions of said tubing into a plurality of helicalcoils with each subsequent coil having a greater outer circumferencethan that of the preceding coil but each subsequent coil having an innercircumference less than the outer circumference of the preceding coil,said helical coils extending in opposite directions from the bend insaid heat exchange tubing to form a continuous tubular member narrow inits center portion and progressively increasing in circumference towardboth ends, and compressing said tubular member from both ends inwardlytoward the center portion to telescope the outer helical coils onto theinner helical coils to form a heat exchanger structure having two rowsto maintain said structure insubstantially' flat shape.

5. The method of manufacturing a heat exchange structure comprising thesteps of providing a short length of heat exchange tubing having amultiplicity of spine sections extending radially outward from thesurface thereof, forming a core member from said short length of heatexchange tubing by reversely bending said tubing and then windingopposite sides of said tubing tightly upon themselves in a directiontransverse to that of said reverse bend, providing two relatively longlengths of said aforementioned type of heat exchange tubing, formingsaid long lengths of heat exchange tubing into a plurality of helicalcoils with each subsequent coil having a greater outer circumferencethan the outer circumference of the preceding coil, each subsequent coilhaving an inner circumference less than the outer circumference of thepreceding coil, connecting the inner ends of each of said lengths oftubing to the ends of said core to form a continuous tubular membernarrow at its center and progressively increasing in circumferencetoward both ends, and compressing the opposite ends of said tubularmember relative to each other thereby to telescope the outer helicalcoils onto the inner helical coils to form a heat exchange structurehaving two rows of coils connected through said core member at theirinner ends and having said spine sections of said heat exchange tubinginterlocking to maintain said structure in a substantially fiat shape.

6. The method of manufacturing a heat exchange structure from heatexchange tubing of the type having a multiplicity of spine sectionsextending radially outward from the surface thereof comprising the stepsof providing a core from a short length of said tubing by reversebending said short length of tubing and then Winding opposite sides ofsaid tubing tightly upon themselves in a direction transverse to that ofsaid reverse bend, connecting first and second lengths of said heatexchange tubing to opposite ends of said core, forming said first andsecond lengths of heat exchange tubing into a plurality of helical coilsextending in opposite directions from said core, each subsequent coil onopposite sides of said core being of greater outer circumference thanthe outer circumference of the preceding coil but each subsequent coilhaving an inner circumference less than the outer circumference of thepreceding coil, said helical coils on opposite sides of said core havingan inner circumference slightly less than the outer circumference ofsaid core, and compressing said coils from said both ends inwardlytoward said core to telescope the outer helical coils onto the innerhelical coils and to move said innermost coils over said core therebyforming a heat exchange structure having two rows of coils with saidspine sections of said heat exchange tubing interlocking to maintainsaid structure in a substantially fiat shape.

7. A machine for manufacturing a heat exchange structure from heatexchange tubing of the type including a multiplicity of spine sectionsextending radially outward from the surface thereof comprising asubstantially pyramid-shaped coil forming fixture including a springlikemember of rectangular cross section helically coiled upon itself withthe smallest coil at one end and with each subsequent coil overlappingonly a portion of the preceding coil, said coils thereby providing acontinuous peripheral tube coiling surface that gradually increases incircumference from end of said member toward the other end, said surfaceof each of said coils being radially displaced from the preceding coilsurface by a small amount less than the diameter of said heat exchangetubing to be wrapped, means for attaching one end of a length of heatexchange tubing onto the smallest coil of said forming fixture, meansfor rotating said coil forming fixture to wrap said length of heatexchange tubing onto said peripheral tube coiling surface of saidforming fixture, a compression plate positioned transversely to the axisof said coil forming fixture adjacent the smallest coil thereof, meansfor moving said coil forming fixture toward'said compression plate, stopmeans attached to successive coils of said spring-like member forcollapsing said spring-like member when said coil forming fixture ismoved toward said compression plate with the smaller coils of saidmember telescoping into said larger coils so that the transverse edgesof said coils cooperate to provide a flat pressing surface normal to theaxis of said coil member thereby compressing said coils of said heatexchange tubing between said compression plate and said pressing surfaceto telescope said innermost coils of said heat exchange tubing withinsaid outermost coils of said heat exchange tubing thereby forming a heatexchange structure having a single row of coils with the spine sectionsthereof interlocking to maintain said structure in substantially flatshape.

8. A machine for manufacturing a heat exchange structure from heatexchange tubing of the type including a multiplicity of spine sectionsextending radially outward from the, surface thereof comprising asubstantially pyramid-shaped coil forming fixture including aspring-like member of rectangular cross-section helically coiled uponitself with the smallest coil at one end and with each subsequent coiloverlapping only a portion of the preceding coil, said coils therebyproviding a continuous peripheral coiling surface that graduallyincreases in circumference from one end of said member toward the otherend, said surface of each of coils being radially displaced from thepreceding coil surface by a small amount less than the diameter of saidheat exchange tubing to be wrapped, means for attaching one end of alength of heat exchange tubing onto the smallest coil of said formingfixture, means for rotating said coil forming fixture to wrap saidlength of heat exchange tubing onto said peripheral tube coiling surfaceof said forming fixture, tube feeding means for maintaining said tubingin alignment with said peripheral coiling surface on said coils of saidspring-like member as said tubing is wrapped onto said surface, acompression plate positioned transversely to the axis of said coilforming fixture adjacent the smallest coil thereof, means for movingsaid coil forming fixture relative to said compression plate, stopmembers attached to successive coils of said spring-like member forcollapsing said spring-like member when said forming fixture is movedtoward said compression plate with the smaller coils of said membertelescoping into said larger coils so that the transverse edges of saidcoils cooperate to provide a hat pressing surface normal to the axis ofsaid spring-like member whereby said innermost coils of said heatexchange tubing are telescoped within said outermost polls of said heatexchange tubing between said compression plate and said pressing surfaceof said spring-like member thereby forming a heat exchange structurehaving a single row of coils with the spine sections thereofinterlocking to maintain said structure in substantially fiat shape.

9. A machine for manufacturing a heat exchange structure from heatexchange tubing of the type including a multiplicity of spine sectionsextending radially outward from the surface thereof comprising asubstantially pyramid-shaped coil forming fixture including a backingplate member mounted for rotation about a substantially horizontal axisand a spring-like member of rectangular cross-section extendinghorizontally outward from said backing plate member, said spring-likemember being helically coiled upon itself with the smallest coil at oneend and with each subsequent coil overlapping only a portion of'thepreceding coil, said coils having their outer surface forming acontinuous tube coiling surface that gradually increases incircumference from one end of said spring-like member toward the otherend, said surface of each of said coils being radially displaced fromthe preceding coil surface by a small amount less than the diameter ofsaid heat exchanger tubing to be wrapped, said spring-like member havingits largest coil thereof at- 7 ll tached to said backing plate memberand adapted to fit within a cavity formed therein to receive saidspring-like member, said cavity having its-outer circumference large;enough to receive the largest coil of said spring-like mem-; ber, meansfor attaching one end of a length of heat ex-: change tubing onto thesmallest coil of said forming fix ture, means for rotating said coil.forming fixture thereby to wrap a length of heat exchange tubing on theperipheral coiling surface of said coils of said spring-like memher, acompression plate positioned parallel to said back 10 ing plate adjacentthe smallest coil of said spring-like member, means for moving said coilforming fixture toward said compression plate, stop members attached tosuccessive coils of said spring-like member for collapsing saidspring-like member with the smaller coils of said member telescopinginto said larger coils and with said larger coil fitting within saidcavity of said backing plate so that the transverse edges of said coilsand said backing plate cooperate to provide a flat pressing surfacenormal to the axis of said coiled member whereby said innermost coils ofsaid heat exchange tubing are telescoped within said outermost coils ofsaid heat exchange tubing between; said compression plate and saidpressing surfaces of said: spring-like member and said backing platethereby forming a heat exchange structure having a single row of coilswith the spine sections thereof interlocking to main tain said structurein substantially flat shape.

10. A machine for manufacturing a heat exchange structure from heatexchange tubing of the type including a multiplicity of spine sectionsextending radially outward from the surface thereof comprising a baseplate mounted on a spindle for rotation about'a horizontal axis, a sub-Istantial pyramid-shaped coil forming fixture having a backing platemovably supported in spaced parallel re lationship with said base plateand having extending hori zontally outward therefrom in a direction awayfrom said base plate a spring-like member of rectangular'cros's-sec tionhelically coiled upon itself, said spring-like member having itssmallest coil at its outer end and having each subsequent coiloverlapping only a portion of the preceding coil, said coils therebyproviding a continuous pe ripheral tube coiling surface graduallyincreasing in cir-' cumference from the outer end of said member towardits connecting end with said backing plate, said surface; of each ofsaid coils being radially displaced from the preceding coil surface byan amount less than the diame ter of said heat exchange tubing to bewrapped, said back ing plate having a cavity therein adapted-tocircumscribe' the largest coil of said spring-like member, means forrotating said'base plate and said forming fixture for 5 wrapping alength of heat exchange tubing on said coil ing surface of saidspring-like member, means for moving said backing member and saidspring-like member away from said base plate, a plurality of stopmembers connect; ing at one end to the individual coils of saidspring-like member and having their outer ends extending to said" baseplate, all of said stop members except said stop members connected tothe smallest coil' of said spring like member being slidably connectedto 'said base plate for permitting limited movement of said remainingcoils 50 of said spring-like member in a direction away from said baseplate during movement of said backing plate away from said base plate,said stop members successively stopping the movement of said remainingcoils as their transverse edges move into alignment with the next pre 5ceding coil thereby causing said spring-like member to present atransverse pressing surface normal to the axis" of said coiling fixture,a compression plate positioned" transversely to the axis of said coilforming fixture ad jacent the smallest coil thereof, said compressionplate and the transverse edges of said coils of said spring-like membercooperating to telescope the innermost coils of said heat exchangetubing within said outermost coils of said heat exchange tubing as saidcoil forming fixtureiis movedaway from said base plate thereby formingaheat i3 exchange structure having a single row of coils with the spinesections thereof interlocking ,to maintain said structure insubstantiallyflat shape. r p

' 11'. A machine for manufacturing a heat exchange structure from heatexchange tubing of the type including a multiplicity of spine sectionsextending radially outward from the surface thereof comprising a pair ofsubstantially pyramid-shaped coil forming fixtures each having a'spring-like member of rectangular cross-section helically coiled uponitself with the smallest coil at one end and with each subsequent coiloverlapping only a portion of the preceding coil, said coils therebyproviding a continuous peripheral tube coiling surface that graduallyincreases in circumference from one end of said member toward the otherend, said surface of each of said coils being radially displaced fromthe preceding ,coil surface by a small amount less than the diameter ofsaid heat exchange tubing to be wrapped, each of said fixtures i beingarranged along a horizontal axis with the smallest coil of each of saidfixtures arranged adjacent each other, means for rotating said coilforming fixtures to wrap separate lengths .of heat exchange tubing ontothe peripheral tube coiling surfaces of said oppositely disposed coilforming fixtures, means for moving said coil form-' ing fixtures towardone another, stop members attached to successive coils of saidspring-like members for limiting movement of said coils ofsaidspring-like members and collapsing said successive coils of saidspring-like members so that the smaller coils of said members telescopeinto said larger coils to align the transverse edges of all of saidcoils of said oppositely disposed spring-like members to provide flatpressing surfaces normal to the axis of said coiled members whereby saidinnermost coils of said heat exchange tubing wrapped on the coilingsurface of said coil forming fixtures are telescoped within theoutermost coils of said heat exchange tubing while said spring-likemembers of each of said fixtures form pressing surfaces moving towardeach other'topress said coils of tubing together thereby forming a heatexchange structure having two rows of coils with the spine sections,thereof interlocked to maintain said structure in substantially flatshape. 7

12. A machine for manufacturing a heat exhange structure from heatexchange tubing of the type including a multiplicity of spine sectionsextending radially outward from the surface thereof comprising a pair ofsubstantially pyramid-shaped coil forming fixtures each having aspring-member of rectangular cross-section helically coiled upon itselfwith the smallest coil at one end and with each subsequent coiloverlapping only a portion of the preceding coil, said coils of each ofsaid fixtures thereby providing a continuous peripheral tube coilingsurface that gradually increases in circumference from,

one end of said member toward the other end, said said oppositelydisposed fixtures, the tube feeding means for maintainingsaidseparatelengths of tubing in alignment withsaid peripheral coilingsurfaces of said springlike members as said separate lengths of tubingare wrapped onto said surfaces thereof, means for moving saidcoil'forming fixtures toward one another, stop members, attached tosuccessive coils .of each of said spring-like members for limiting themovement of said successive coils of said spring-like members Whensaidforming tures are moved toward one another so that saidsmaller coils ofeach of said spring-like members telescope into said larger coils toalign the transverse edges of said coils ofoppositely disposedspring-like members to pro vide fiat pressing surfaces normal to theaxis of said coil members whereby said innermost coils of said heatexchange tubing are telescoped within the outermost coils of said heatexchange tubing while said spring-like members of each of said fixturescollapse to form pressing surfaces moving toward each other to presssaid coils of tubing together thereby forming a heat exchange structurehaving two rows of coils with the spine sections thereof interlocked tomaintain said structure in substantially flat shape.

References Cited in the file of this patent UNITED STATES PATENTSStambaugh Aug. 15, 1905 Humphrey Dec. 2-8, 1915 Price Feb. 19, 1924Summers Apr. 21, 1931 Bilger et a1 May 2, 1939

